1. Field of the Invention
The present invention relates generally to CATV distribution systems and more specifically, to a signal splitter device for the distribution and re-combining of CATV downstream and upstream signals having a substantially expanded range of frequencies across two or more output ports associated with the device.
2. Discussion of the Related Art
The nature of typical cable television (CATV) distribution systems is such that the downstream signal carried on the signal transmission line has to be split and re-split many times in order to be distributed to a plurality of receivers from a common signal insertion point. The splitting of the downstream signal is effected by specific electronic devices, typically referred to as signal splitters, installed at specifically spaced locations across the cable plant. In the upstream direction, signals from any potential insertion points should combined at the splitter. In the head-end, signals from individual signal sources are combined to create a common downstream spectrum while downstream signals are split to feed receivers for each service.
The signal splitters that divide the signals among the outgoing CATV network branches must provide several important performance characteristics. The most important characteristic concerns transmission and distribution of a signal having a bandwidth spanning a wide range of frequencies. Currently, a standard CATV signal has a typical bandwidth ranging from about 5 MHz to about 1000 MHz (1 GHz). In the system and method proposed by the above-referenced related invention the substantially expended bandwidth of the CATV signal will include frequencies up to about 3 GHz or higher. At those substantially extended ranges of frequencies, conventional components of the signal splitters do not perform. Another performance standard concerns RF power loss. While being transported across the cable plant from the CATV head-end to the subscriber's premises equipment the signal typically passes through several splitter devices. As any attenuation in a splitter will be multiplied by the number of splitters in the system the signal insertion loss must be uniform over the extended range of frequencies within a small fraction of the decibel. In addition, a CATV splitter must provide good input/output return loss. Therefore, any signals flowing back from one of the output branch circuits should be absorbed by the splitter and not reflected back down the branch circuit. Furthermore, a CATV signal splitter should provide good output isolation. This means that the signal entering or exiting one of the output ports should not appear at another output port. In addition to standard splitter characteristics the CATV signal splitter have to include AC power-passing capabilities by selectively providing current-limited power supplied by a line AC current power inserter along with the RF to the components of the system, such as the amplifiers and the subscriber's premises equipment. Power should be passed through the splitter and be passed to one or more output ports of the signal splitter.
There is therefore a need for a signal splitter which will meet the above-mentioned operational characteristics when operating at a substantially expended bandwidth, which includes usable frequencies up to 3 GHz or above.